Dielectric heating apparatus



Dec. 30, 1952 w. H. ANDERSON DIELECTRIC HEATING APPARATUS 5 Sheets-Sheet 1 Filed Jan. 20, 1950 1,111,, IIIIIIIIII INVENTOR 56 William H. Anderson.

ATTORNEY Dec..30, 1952 w. H. ANDERSON 2,623,982

DIELECTRIC HEATING APPARATUS Filed Jan. 20, 1950 3 Sheets-Sheet 2 Fig.2.

I I E E F |2e $3 1 I26 I24 p 50 42 5 54 m k 72 T a E k ll "-Q f l I08 90 m 82 E is F|g.4. 44 I02 52 10s 54 5s "m l WITNESSES: INVENTOR William H. Anderson.

BY 4 772v- M -i f f Dec. 30, 1952 w. H. ANDERSON 2,623,932

DIELECTRIC HEATING APPARATUS Filed Jan. 20, 1950 I5 Sheets-Sheet I5 IN'VENTOR /a. ATTORNEY William H. Anderson.

.heating electrode.

Patented Dec. 30, 1952 DIELECTRIC HEATING APPARATUS William H. Anderson, Elkridge, Md, assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application January 20, 1950, Serial No. 139,547

1.3 Claims. 1

My invention relates to dielectric heating apparatus for dielectrically heating a plurality of workpieces.

More specifically, my invention is directed to dielectric heating apparatus which comprises a complete self-contained unit. Such a unit generally includes a pair of relatively insulated heating-electrodes between which the work is placed for heat-treatment. The heating-electrodes are energized from a high-frequency power supply that comes from a generating system carried in a casing of the unit; the generating system usually comprising electronic tubes and high-frequency circuits, as is known to the art.

In the smaller sized units, the associated heating-electrodes are usually two small parallel plates, or the equivalent, arranged one above the other so to provide an upper and a lower heating-electrcde. The upper heating-electrode is preferably carried on a pantographic linkage which assures that it will always be substantially horizontal. The pantographic linkage provides a flexibility which permits the unit to be used for heating batches of work of different heights and under different conditions, such as, for example, with different widths of air-gaps above different batches of work.

In order to prevent high-frequency radiation and to provide apparatus in which the work can be quickly and safely heat-treated, and for other able with respect to each other, one of them usually being a part of or secured to the casing of the unit and also supporting the pantographic linkage. Apparatus of this kind, comprising a cage-structure consisting of two cage-members which are hinged together along a side, is shown in United States Patent No. 2,498,632 to W. H. Anderson and D. S. Shingler.

Wheii the work consists of a plurality of small pieces or objects, considerable time may be required to lead and unload the work from a dielectric heatin unit if each piece is placed separately in the unit. According to my present invention, one of the cage--nembers is a drawer which remoyabiy slides into and out of the other cagemember. In accordance with my invention, the removable drawer has a work-supporting floor or hot-tom that may be fixed to or placed on the drawer, this floor or bottom constituting the lower This makes it possible to use r a plurality of drawers so that one or more of them can be loaded with Work outside of the unit during the time that another is in the unit with the work carried thereby being heated dielectrically.

The upper heating-electrode in my present preferred form of apparatus is carried by a linkage in such a manner that it can be moved so as not to interfere with movement of the drawer. However, the mechanism for moving the upper heating-electrode can be used to place it back in proper operating position after the drawer reaches closed position.

An object of my invention is to provide a unit having a drawer-type cage-structure of a type described.

A further object of my invention is to provide a drawer-type cage-structure of a type described having a stationary or fixed cage-member that is electrically grounded or connected to the casing of the unit.

A further object of the invention is to provide a drawer-type cage of a type described, which has an upper heating-electrode that is insulatedly carried by the fixed cage-member.

Still another feature of my invention is the provision of a drawer-type cage of a type described, having means which presses the two cage-members together, in closed position of the cage, so as to assure good electrical contact between the drawer and the fixed cage-member so that the drawer can constitute a grounded heating-electrode.

A further feature of my invention is the arrangement of an operable means which can be operated from outside a closed cage of the drawer type described, to lock the drawer in place and to unlock it. The operable means extends into the cage and cooperates with the mechanism which places the upper heating-electrode in its desired positions. The operable means is so arranged that the energy from the unit can be applied to the work between the heating-electrodes 7 only when the drawer is so locked in place and the upper heating-electrode is in its lower, operative position.

Objects, features and innovations of my invention, in addition to the foregoing, will be discernible from the following description of a preferred embodiment thereof. This description is to be taken in conjunction with the accompanying drawings, on varying scales, in which:

Figure 1 is a vertical sectional View of an upper part of a self-contained dielectric heating unit embodying the principles of my invention, show- 3 ing the drawer cage-member partly withdrawn;

Fig. 2 is a similar view of the unit showing the drawer in closed, locked position;

Figs. 3 and 4 are horizontal sectional views substantially on the lines IIIIII and IVIV, respectively, of Fig. 2;

Fig. 5 is a front View of the cage;

Fig. 6 is a partial side view looking in the direction of the. line vVIVI of Fig. 5 of the cage;

Fig. '7 is a sectional view substantially on the line VIIVII of Fig. 3; and

Fig. 8 is a greatly simplified explanatory wiring diagram of a control circuit utilizablein the unit.

Referring more particularly to-Figs; 1 and-t, a top wall 2 very sketchily represents'the outer metallic casing 2 of a high-frequency generating unit that includes equipment, within the cas ing, for generating high-frequency power. .A suitable circuit for delivering the high-frequency power-includes aninsulated conductor .4 which passes centrally. through an. insulating. bushing 6.

in the. top wall-2..

The -top wall 2 carries a two-part.metalcage The second part of the cage-structure comprises a movable cage-member in the formof a drawer which'is referred. toin its entirety'by the reference'numeral" 24. The drawer is metallic and comprises a fiat' work-supporting bottom wall or floor 2'5 and a front wall 28 held together in any suitable mannerby means such as gusset plates 259.. Thefront'wall 23Jis adapted t'o'close the'opening 22 when the cagelisclosed. The drawer 24 slides into and'out of the other cagemember [8 on drawer-engaging means in the form of spaced horizontal angle-rails..3i'i and 32 fixed to the cage-member iii. The rails 3il and 32 are arranged symmetrically with respect to the bushing 6, so that the bottom 26 is over the bushing in closed position of the cage, but is spaced from the bushing for air-insulation; Work to .be

heat-treated is placed onthis bottom or floor '26 which constitutes a lower.heating-electr.ode 26 for the dielectric heating'unit in'its entirety;

Work on the "drawer-fio'oixori lower heating:v electrode 26 is heated by a high-frequency.electric field establishedbetween thislower'heating-H electrode Ze'and'an'upper heatingeelectrode 36' by a support means carried'by the :fix'ed cage-.

member-it; The support-means compriseslinks of a pantographic linkage 36, a fioatingend member 38, andone or more insulating post ddwhich.

depend from the end membe'rtB-to which the heating-electrode is secured;

The pantographic linkage is constructed along the lines described'intheaforesaid United States Patent No. 2,498,632 and comprises two pairsrof vertically-spaced, generally horizontal,

tiltablelinks iE -and' ea 5 One-pair of'vertically 4 spaced link 42 and 44 has its back ends pivotally connected to an end wall 45 of the end member 38, and the other pair of links has its back ends similarly pivotally connected to the opposite end wall 48 of the end member 3%. The other, or front, ends of the links are secured to shafts 58 and 52 which are rotatably mounted in a pair of short vertical bars fi i that are secured to spaced vertical cam-plates 56. These shafts 59 and 52 and bars 54 form an end member for the pantographic linkage 36.

The cam-plates 56 are part of the fixed cagemember It; being near the side walls l2 and Hi thereof.- Each-cam-plate 56 extends, preferably,

forthe' height of the cage-member I8 and has a back edgev 5.8.:whichslopes vertically, going frontward as it goes downward.

The pantographic linkage 36 has a biasing means in the form of a tension spring 62 near one set of links and a tension spring 64 near the other set, asshown in.Figs.,,1-3. These springs have. their..-front .ends..anchored..on the upper shaft 59. a lower pivot means 66, carried by the .walls andx ld-ofthe end .member38, andto'which the floating ends of the lower .links M are pivotally secured. With this arrangement the biasing ineans-comprisingthe springs 62 and 6% tends to turn thepantographic' linkage so that its links turn counterclockwise with respect to the axes of the shafts 5% and 52. This means that the floatingends of the links, the end member 3 3, the insulatingmembers .40 and theupper heatinge electrode 34 also tend'to'move in an upward direction for raising theheating electrode at. Any suitable stop means canbe provided for limiting such upward movement" of the described assembly.

In accordance with my invention, an operating mechanism :or means'lowers the'upper heatingelectrcde 34 to operative position above the drawer-floor or loweriheating-electrode .25 after the drawer 2d.is closed; This operating means comprises. a pair. of drawer-handles .76 and ii that can be grasped for sliding thedrawer or movable cage-member 24 into and out of the fixed cage-member Ill. The drawer-handles are accessible from outside thecageand are near the sides of the front wall 28 of the drawer 2 3, being mounted inv the front wall by iournalling means id and 76,r,espectively.

Eachhandle and its .journalling means is the same as theothe'nso .thatthis. description is limitedto one .of .them. Each handle comprises an outengra'spi-ngportion..and.a horizontal shaft portion 33 extendingat. substantially a rightangle,. therefrom. The...shaft.portion TF3 passes through the front. wall za andis .rotatably held in. a hearingtfl. of the. .associatedjournalling means; The bearing .is fixed to .therear. of the.

front wall 28 ofthe draweridisoas. to .be nearv the edge 53 of a cam-.platetifi when the cage is closed.

The. front orputerpart. of the shaft-porticn 'Efi'ha's fixedthereto Ia (10112382... The back end .of the shaft-portion i8 hasfixed thereto an operating'inember. in theifor'miof a rodt l which extends 'perpendicularly'from the shaft-portion it and in the same plane as the grasping portion.

"1 The operating rod. 84 has a shorter end (it extending outward from .one side of the shaft-portion Wanda hmgeriend E3 extending outward from the .other.

A compressionspring 5%, between the collard? and thefront wall 2 3. of theldraw er '2 i, tendsfto Their opposite'ends are anchored on push. the handle; forwardly, but: the extent: of such motion isilimitedby. theopera-tingrod 84 enber II), when the cage is closed, the handles l3.

and I2 are turned so that their grasping portions are vertical, thereby placing the operating rods $4 vertically. For'locking the drawer, the hantiles are then turned so that the rods 84 move to horizontal positions. The directionof rotation of the handles is such. that the longer ends BBofthe rods 84i move toward the side walls I2 and I4 of the fixed cage-member Iii. 84 are long enough so that their ends 88 pass through slots 92 in-the side walls. In such horizontal position, the ends 83 engage and closeinterlockswitches 94 secured to the outsid'esof the side Walls, I2 and I4. In any other position of the ends 88- the switches 94 are open.

In moving to the horizontal position described,

each end 83- also rides upwardly on the edge 58- of the adjacent cam-plate 55, thereby locking,

the drawer closed. Since the width of'the camplate increases in the upward direction, the associated, drawer-handle is forced backward, compressing the spring 98 and forcing the front wall 28, of the drawer 24 rightly against the front wall I8 of the cage-member Iii. In this way the electrical contact between the floor or lower heating-electrode 26 of the drawer 24. and the fixed cage-member ID is made better, and augments the electrical contact between the bottom or lower heating-electrode 26 and, the metal rails. 39 and 32' on which, it rests. The edges 58 of the cam-plates 56 have. shallow positioning notches 96 at the horizontal positions of the rods 34, as shown in Fig. 6..

After the drawer is closed, theupper heating electrode 34- is lowered to an operative position by means extending outside the closed cage. In accordance with the preferred form of my invention, this is done simultaneously with locking of the drawer andby the same operating means comprising, more specifically, a handle orhandles I0 and 52. To this end, the shorter end 86 of the operating rod 84 of each handle is effective.

Each shorter end 85 of a rod- '64 rides on a pulldown arm Hid which is loosely rotatably carried on. the, lower shaft 52 of the pantographic linkage 36. Each arm Iiiil is generally in the shape of a right angle and has a lower arm member m2 adapted to be engaged by the associated end 83' as the end turns; from vertical to horizontal position when the associated handle is turned to lock the drawer 24. As an end 86 of the rod 84 engages the arm portion H32, it causes the pulldownarm to move forwardly, that is, clockwise on the shaft 52 with respect to Fig. 2.

Each arm I08 has a tension spring Hid that has an end secured to the lower link 44 at a point intermediate the pivot points 52 and 65, and another end attached to the end or" the arm member I02.

Normally, with the drawer Z 1 unlocked, the bias of the springs I64 on the pantographic linka e. 36 is less than. that of th spr n s 6.2 and E4 so that th upper h atin -e ec rode i rais d position. When a handle is turned, it forces the end 86 of the associated rod 84 downwardly, turning the arm Iiii] and extending spring IE4. The increased force overcames the springs 62 and The rods 6; 64; so that the; upper heating-electrode 34 drops. Lugs IDS-and l 08" on the-pull-down arms and links; 44, respectively, keep "the; arms and links in proper position.

The interlockswitches 94 con-trol the application of high-frequency energy-to the heatingelectrodes 26 and 34-. Suitable electrical connections forrtheunit areshown in simplified form in Fig. 8. When engaged by the end-portions 88 of theoperating rods 84, the switches 94, in series, closea circuit I Ill toa relay II2thatoperates to close the power-supply-circuit; I I4 that supplies power to the generating equipment inside the casing 2. Consequently the conductor 4 is energized. Obviously, the switches 94 cannot be closed by the end-portions 84 unless, the drawer 24 is in closed position, with its bottom wall or lower heating-electrode beneath the upper heating-electrode 3,4.

It is to be noted that the upper heating-elem trode 34 is carried bythe stationary cage-meme her; I0, but is insulated therefrom by the insulatingposts 43'. To convey high-frequency power to the upper heating electrode, a connector H3 is provided; having an end attached to the com ductor 4. This connector is shaped to pass around the innermost end of the drawer in closed position, as indicated in Fig. 2, and terminates in a bowed. resilient strap H8 that is tightly fastened to the upper heating-electrode 34. As the upper heating-electrode 34 moves between its upper and lower positions, the strapbends into different shapes.

The. high-frequency path or circuit i completed through any suitable grounding means that includes. the metal of the cage-structure 8, and of the casing 2-. Since this path must necessarily include a portion that passes from the bottom or lower heating-electrode 26 to the stationary cage-member II], the provision for intimate electrical contact between the drawer 24 and the cage-member I I3, resulting from the end-portions 83 of the rods 84 engaging the cam-plates 56, assures a satisfactory path for the high-frequency. current.

Assuming that the drawer is to be unlocked, the handles 10 and I2 are turned to place their outer grasping portions vertically. The longer end-portions 88 of the operating rods 84 attached to the handles, first release the interlock switches 94, thereby opening the circuit I II! which in turn opens the power-supply circuit H4 for the highfrequency equipment in the casing 2. Hence, the heating-electrodes 26 and 34 are deenergized.

- The longer end-portions 88 then pass through the slots 92 and into thev cageestructure 8. Simultaneously the shorter end-portions $5 of the operating rods 84 move away from the pull-down arms I60 so that the, biasing means, comprising the springs 52 and 64,, can move the upper heating-electrode upwardly. Accordingly, the drawer 24 and work thereon can be freely removed and another similar drawer with work, thereon inserted. '4 7 A. ieature at my invention isv the nrovisic of mean that permi -s the lowermost ope ating posi tion of he, upp r h atin -el c ro 3 t r determined, without interfering with the mechn sms an p ie ie s d sc ibedhis means comprises the sprin s, "J4 that are associated w th he ull-d n arms we n comprises adjusting means near the top and front ol the cageestructure 8 and indicated in its entirety by the reference numeral I 20, I I I V h ad usting m an 29 compr ses a screw rod I22 having a threaded portion rotatably carried in a-threaded bearing 124 in the front wall 18 of the fixed cage-member as, and an adjusting knob I26 outside of the cage. The inner end of the threaded portion carries a manually adjustable stop nut [28. The rod 122 passes through an enlarged hole in a small plate I33 that is centrally fixed to the upper shaft 53 of the pantographic linkage 35. By adjusting the position of the nut I28 backward or forward, the plate moves clockwise or counter-clockwise with respect to the shaft 58, carrying the pantographic linkage with it.

Ordinarily, the biasing means comprising the springs 62 and st raises the upper heatingelectrode 3 3 so that the plate 530 is away from the nut I28, as shown in Fig. 1. However, when one or both of the handles It and '52 are turned, for locking the drawer 25 closed, their operating rods 84 turn the pull-down arms 1B which act through the springs iil i to pull the linkage 35 downward and move the plate E3d toward the positioning nut l28. Assuming that the lowermost position which the upper heating-electrodeis to reach is above the work on the drawer bottom 26, the plate I39 reaches and engages the nut I28, as shown in Fig. 2; and the pantographic linkage 35 and upper heating-electrode stop in a position which depends on the adjustment of the nut I28. Continued movement of the handles iii and i2 merely stretches the springs id i. Usually,- the metal of the cage-structure is perforated and the adjustment obtained by tuning the knob I25 can be seen through the perforations.

While I have described my invention in a form preferred, it is obviously subject to wide variations, and its principles are applicable in other embodiments.

I claim as my invention:

1. A dielectric heating apparatus of a type described comprising a pair of relatively insulated heating-electrodes, a metallic cage about said heating-electrodes, said cage comprising a pair of cage-members, one of said members being relatively movable with respect to the other to open and close the cage, whereby the cage may be loaded with work to be heated and the heated work unloaded, said movable cage-member carrying a first of said heating-electrodes, and pressure-applying means comprising a cooperative part carried by a first of said cage-'nembers, a cooperating part carried by a second of said cagemembers and a cooperative part carried by one of said heating-electrodes, said pressure-applying means being operable for pressing said cage-nembers firmly together with said heating-electrodes properly positioned and spaced to provide a workheating space therebetween.

2. Apparatus as defined in claim 1 but further characterized by said one of said parts comprising a sloped surface and another of said parts comprising a member ridable thereon, said sloped surface being positioned respecting said ridable member such that the pressure is effected thereby.

3. Dielectric heating apparatus comprising, in combination, a pair of relatively insulated heating-electrodes, a first of said heating-electrodes being above a second of said heating-electrodes, a cage, means supporting said first heating-electrode inside said cage, said means comprising a pantographic linkage including a pair of vertically spaced, generally horizontally extending links, a floating end member to which ends of said links are pivoted, said end member carrying said g. first heating-electrode, support means carried by said cage pivotally carrying the other ends of said links, and a pair of biasing force-exerting means associated with said pantographic linkage, said pair of biasing means acting to turn said pantographic linkage in opposite directions, a first of said biasing means being stronger than the second.

4. A dielectric heating apparatus as defined in claim 3 but further characterized by each of said biasing means comprising a spring attached to said pantographic linkage at a point removed from said support means.

5. Dielectric heating apparatus comprising, in combination, a pair of relatively insulated heating-electrodes, a first of said heating-electrodes being above a second of said-heating-electrodes, a cage, means supporting said first heating-e1ectrode inside said case, said means comprising a pantographic linkage including a pair of vertically spaced, generally horizontally extending links, a floating end member to which ends of said links are pivoted, said end member carrying said first heating-electrode, support means carried by said cage pivotally carrying the other ends of said links, a pair of biasing force-exerting means associated with said pantographic linkage, said pair of biasing means acting to turn said pantographic linkage in opposite directions, a first of said biasing means being stronger than the second, and force-augmenting means operable to increase the force of said second biasing means so as to overcome the power of said first biasing means.

6. A dielectric heating apparatus of a type described comprising, in combination, a pair of relatively insulated heating-electrodes, a first of said heating-electrodes being placeable in operat" ing position above a second of said heating-electrodes, a cage about said heating-electrodes, said cage having a first member and a second member which are relatively movable so that work to be heat-treated can be placed between said heatingelectrodes, a linkage in said cage comprising a first member carrying said first heating-electrode, and a second member carried by a first of said cage-members, biasing means associated with said linkage and tending to move said irst heating-electrode in a predetermined direction, and electrode-positioning means comprising a first part carried by said first cage-member and a second part carried by said second cage-member and operable against said biasing means to move said heating-electrode in a direction opposite to said predetermined direction.

'7. Apparatus as defined in claim 6 but further characterized by said first part comprising a pulldown arm and a spring connecting said arm to said linkage, and said second part comprising a member engaging said arm to move it against the action of said spring.

8. Apparatus as defined in claim 7 but further characterized by said linkage being a pantographic linkage, and by said biasing means tending to move said linkage and said first heatingelectrode in a direction away from said second heating-electrode.

9. A cage-structure for dielectric heating apparatus of a type described, comprising wall means including an outer metallic front wall, said wall means providing a drawer-opening having an entrance-portion in said front wall, a drawer slidable in said opening and having a work-receiving bottom adapted to provide a lower heating-electrode, said drawer having a front wall adapted to close said entrance-portion and a drawer-operating handle movably carried by said drawer-wall, an upper heating-electrode inside said cage-structure, biasing force-exerting means tending to hold said upper heating-electrode in raised position above its operating position with respect to said bottom, and a mechanism operated by said handle and associated with said biasing force-exerting means for lowering said upper heating-electrode, said upper heating-electrode being supported inside said cage-structure by a pantographic linkage, and said mechanism having an operating member operated by said handle and a cooperating pull-down member associated with said pantographic linkage, the last of said member being engageable by said operating member, in closed position of said drawer, for lowering said upper heating-electrode.

10. A cage-structure for dielectric heating apparatus of a type described, comprising wall means including an outer metallic front wall, said wall means providing a drawer-opening having an entrance-portion in said front wall, a drawer slidable in said opening and having a work-receiving bottom adapted to provide a lower heating-electrode, said drawer having a front wall adapted to close said entrance-portion and a drawer-operating handle movably carried by said drawer-Wall, a floating end member inside said cage structure, an upper heating-electrode, said end member comprising a depending support carrying said upper heating-electrode over and relatively insulated from said bottom, vertically spaced, horizontal links having ends pivotally secured to said end member and other ends pivotally held by said wall means at a point above said drawer-opening, biasing force-exerting means tending to keep said links and upper heating-electrode in raised position, a pull-down arm loosely connected to said linkage on the side toward said outer front wall, and mechanism comprising an operating rod attached to said drawerhandle and operable by movement of said drawer-handle to tend to force said pull-down arm 10 downwardly so as to lower said links and upper heating-electrode to an operative position above said bottom.

11. A cage-structure as defined in claim 10 but further characterized by a spring connected to said pull-down arm and said links, said pulldown arm having a sloped surface on which said operating rod rides and forces said drawer downwardly.

12. A cage-structure as defined in claim 10 but further characterized by adjustable stop means determining the lowermost point of said operative position of said upper heating-electrode.

13. A cage-structure as defined in claim 12 but further characterized by said adjustable stop means comprising a plate, and a rod means engaging said plate and passing through a wall of said cage-structure.

WILLIAM H. ANDERSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,442,451 Albin June 1, 1948 2,497,945 Jennings Feb. 21, 1950 2,498,632 Anderson et a1 Feb. 28, 1950 2,594,956 Atwood Apr. 25, 1950 2,512,751 Proctor et a1 June 2'7, 1950 2,528,492 Bradley et al. Nov. 7, 1950 FOREIGN PATENTS Number Country Date 607,572 Great Britain Sept. 1, 1948 613,643 Great Britain Dec. 1, 1948 OTHER REFERENCES Redifon Heater, Electronic Engineering, October 1948, page 332. 

